Rear pinion angle

[WILDHOBO]

And the answer is - the height of the front doesn't matter. It's all in the angle of the joints and/or pinion.
Dan's been through this if I remember.
Single cardan joints need to be run straight (meaning if there's just one cross type joint on that shaft), if there's one at each end of the shaft, they need to cancel each other. Driveshafts 101.
Pitch of the truck doesn't matter for pinion or driveshaft angles. Raising the front up a foot won't fix poor pinion angle or improper driveshaft cardan joint angle.

I wouldn’t have known at all 2 years ago, but now I know this is absolutely correct. Thanks to Shadows for his advice before my first go around. It made it easier for sure.

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[ducatijosh]

Whether the angle is “poor” or not is not what OP asked. You’re saying on an incline (we’ve discussed this earlier today) where the nose is pointing down, the pinion won’t also be pointing down?

OP please wake up and clarify your question for us LOL

Yeah I guess I’m not sure If when I lift the front tomorrow and then get it on flat ground if the pinion angles will be all better or if I need to adjust the rear control arms to fix it. I measured like 5 times and all 4 rear arms are exactly what is notated in the Clayton lift documentation. Just seems odd that the angle is so far off. The truck has a massive rake as it sits currently.

 

[WILDHOBO]

Yeah I guess I’m not sure If when I lift the front tomorrow and then get it on flat ground if the pinion angles will be all better or if I need to adjust the rear control arms to fix it. I measured like 5 times and all 4 rear arms are exactly what is notated in the Clayton lift documentation. Just seems odd that the angle is so far off. The truck has a massive rake as it sits currently.

The rake, and the front lift, have no bearing on the rear, as @ShadowsPapa stated. If you want to fix the rear, the control arms are the best way. The carrier bearing spacers are great as a companion to the fix, but do not resolve it completely.

 

[Rusty PW]

Install the front lift and look at your pinion again. Optics are playing with your eye sight.

Did you put an angle indicator on the housing for before and after readings? The readings will change when you lift the front.

 

[Lunentucker]

It'll last a long time as it is, but if and when it fails ...

 

[WILDHOBO]

Install the front lift and look at your pinion again. Optics are playing with your eye sight.

Did you put an angle indicator on the housing for before and after readings? The readings will change when you lift the front.

The front height has no bearing on the rear pinion angle.

 

[ShadowsPapa]

The front height has no bearing on the rear pinion angle.

Exactly, you beat me to it. With that big a lift on the rear, the pinion is indeed tipped. The upper and lower control arms swing in different arcs so once they are swung far enough down at the rear, the longer arm moves forward less than the shorter arm, tipping the whole axle assembly. The bigger the lift, the more the tip.
You have also dropped the axle down in relationship to the driveshaft, thus the bearing spacer to lower the shaft down and decrease the rear joint angle.

This is why if you have a single cardan u-joint you want to minimize the angle at which it operates, keep the pinion lined up with the shaft as much as possible -

And the above is why when you have a cardan joint at each end of a shaft, they need to be in phase and as close as possible to the same, but opposite, angles so the rotational speed differences cancel each other out.
It's not a concern on CV joints as there's no difference in rotational speed as the shaft turns.
But it's a huge thing on cross type, or cardan joints.

I've got magnetic electronic angle gauges, and from my time in the shop in the 1970s, I have the Miller tool we used back then, and this scan of the instructions -

Pinion angle is important more as it relates to its relationship with the driveshaft - and that can be more or less critical based on the types of joints being used.
If that rear joint is a cross or cardan type and the only one on that shaft, that angle is very important.

 

[ShadowsPapa]

It'll last a long time as it is, but if and when it fails ...

I'd call that epic fail.......

Various CV joints can handle a heck of a lot more angle and don't need to be matched end for end, but they also have limits - isn't it somewhere in the 30s as far as degrees? Memory failing..........

 

[Pescatoral Pursuit]

To correct pinion in the rear, shorten lowers and lengthen uppers, the exact same amount. I’d start with 1/4” on both. That will help your pinion angle without changing wheelbase.

How much play is in the driveshaft to be able to adjust the top CA only?
If you try to adjust both control arms equally in and out while adding lift, then the wheelbase is shortening.

 

[ShadowsPapa]

How much play is in the driveshaft to be able to adjust the top CA only?
If you try to adjust both control arms equally in and out while adding lift, then the wheelbase is shortening.

The lift alone shortened it as the arms swung down and forward, although each swinging a different distance, but still, forward - so yeah, the axle is now closer to the front by virtue of a high lift.
(good idea to measure center of hub to some given point on the truck before a major lift to assess how far forward the whole axle moved due to the swing down and ahead of the arms)

 

[WILDHOBO]

How much play is in the driveshaft to be able to adjust the top CA only?
If you try to adjust both control arms equally in and out while adding lift, then the wheelbase is shortening.

Depends on the driveshaft, but a lot. My suggestion is assuming you’re happy with your current rear axle position in the wheel well. Mine is really close to dead center.

 

[WILDHOBO]

The lift alone shortened it as the arms swung down and forward, although each swinging a different distance, but still, forward - so yeah, the axle is now closer to the front by virtue of a high lift.
(good idea to measure center of hub to some given point on the truck before a major lift to assess how far forward the whole axle moved due to the swing down and ahead of the arms)

I think people are thinking this moves axles by inches. It really doesn’t. These are pretty small front to back movements from a wheelbase standpoint.

Edit: and a slightly shorter wheelbase actually helps in high centering situations.

 

[ShadowsPapa]

I think people are thinking this moves axles by inches. It really doesn’t. These are pretty small front to back movements from a wheelbase standpoint.

Edit: and a slightly shorter wheelbase actually helps in high centering situations.

Fractions, not multiple inches. Pretty easy to pencil out if one knows the length of the control arm and how far down one end swings. One can also calculate the amount the pinion would "tip" based on the differences of the lengths of the control arms (upper vs lower)

Good to know 1/4" will help me get over that next boulder - maybe taller tires would make some difference, too LOL (and look better with that big a lift)

Hey, are we now picking nits? I wonder if John Deere makes a nit picker.

 

[jav_eee]

Install the front lift and look at your pinion again. Optics are playing with your eye sight.

Did you put an angle indicator on the housing for before and after readings? The readings will change when you lift the front.

Everyone read “pinion angle” and hyper focused on that. The fact that he lifted the rear first is playing games with his eyes. Obviously lifting the front won’t affect the pinion angle as it’s already set by the control arms but lifting the front of the vehicle WILL move the pinion angle up a little since the whole vehicle will be rotating up at the front. Like I said earlier, I wish OP @ducatijosh would clarify this for the class!

 

[ducatijosh]

Everyone read “pinion angle” and hyper focused on that. The fact that he lifted the rear first is playing games with his eyes. Obviously lifting the front won’t affect the pinion angle as it’s already set by the control arms but lifting the front of the vehicle WILL move the pinion angle up a little since the whole vehicle will be rotating up at the front. Like I said earlier, I wish OP @ducatijosh would clarify this for the class!

Sorry I’m not not good at this or explaining. I want the drive shaft to be pointed at the center of the pinion hole not coming in at an angle. Yes the front of the Jeep is super low in this picture. Does that affect what I’m looking at? I’m installing the lift on the front as we speak and will report back when all done how things are looking. I just want to be able to safely drive this to an alignment shop without chewing up something.

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